1. Field of the Invention
The present invention relates to a circuit breaker having vertically aligned line and load terminals coupled to quick disconnects structured to engage a bus assembly having vertical risers interspersed with horizontal runbacks and, more specifically, to an offset assembly structured to be couple to the line and load terminals to align the quick disconnects with the alternating vertical risers and horizontal runbacks.
2. Background Information
Low voltage circuit breakers used in electric power distribution systems are commonly mounted in a housing assembly and supported on rollers which permit easy installation and removal of the sizeable circuit breakers required for such service. The housing assembly has walls forming an enclosure and a bus assembly. The bus assembly includes line and load conductors for each pole of the circuit breaker. Each line conductor, or “riser,” is, essentially, an elongated conductor bar with the longitudinal axis extending vertically through the housing assembly. That is, the vertical riser typically extends both above and below the circuit breaker so that other components may be coupled to the vertical riser. Because the vertical riser extends both above and below the circuit breaker, the load conductors must be offset relative to the vertical risers. The load conductors, or “runbacks,” are elongated conductive bars extending from the back of the housing assembly toward the front of the housing assembly. The runbacks are typically interspersed, and offset laterally, with the line conductors. The conductor bars are structured to be engaged by quick disconnects, which are coupled to terminals on the back of the circuit breaker, as the circuit breaker is moved into the housing assembly.
As discussed herein, and as shown in the Figures, the circuit breaker is a three-pole circuit breaker, however, it is understood that the invention may be practiced with a circuit breaker having any number of poles. Where the circuit breaker is a three pole circuit breaker, the bus assembly includes six conductors—three line conductors and three load conductors. A non-conductive shroud is disposed about the bus assembly conductors to provide support and resist accidental contact between the line and load sides of the circuit.
The circuit breaker includes one pair of terminals for each pole of the circuit breaker. The terminals include a line terminal and a load terminal. The terminals are, typically, horizontally flat members made from a conductive material. Additionally, the line terminal is normally disposed directly above the load terminal. In order to couple the circuit breaker to each conductor in the bus assembly, the quick disconnects must be aligned with the vertical risers and runbacks.
To enable the circuit breaker to engage the bus assembly, the issue of alignment of the quick disconnects with the bus assembly conductors has been addressed as follows. One solution has been to have the vertical risers and runbacks vertically aligned. That is, the vertical riser has been adapted to include an opening to allow a runback to extend therethrough. Where the vertical riser has a suitable shape, for example, a U-shape, the vertical riser bight may have an opening therethrough. In this configuration, the runbacks are not offset from the vertical risers and instead pass through the opening. Thus, a quick disconnect coupled to a vertically aligned pair of terminals would also be aligned with the vertically aligned vertical risers and runbacks. This design, however, incurs more production costs than the use of a solid riser and is prone to overheating where the cross-sectional area of the vertical riser is reduced.
Moreover, as noted above, a typical bus assembly included runbacks that extend in between, or, as to the last runback in the assembly, to one side of, the vertical risers. As such, the conductors in the bus assembly are not typically aligned vertically. Thus, the circuit breaker could be structured with offset terminals. However, as also noted above, a typical circuit breaker has the line terminal and load terminal for one pole of the circuit breaker aligned vertically. Thus, as shown in U.S. Pat. No. 6,040,976, to couple each terminal of a circuit breaker to a conductor, a bent stab device and a set back conductor were utilized. That is, either the line or load terminals of the circuit breaker were aligned with the appropriate type of conductor. For example, the load terminals were aligned with the load conductors. The other terminals, in this example the line terminals, had a bent stab coupled thereto. The bent stab had an elongated length which included an angled medial portion. To provide room for the length of the bent stab, the vertical riser was set back in the housing. Thus, the circuit breaker load terminal quick disconnects were coupled directly to a runback whereas the circuit breaker line terminal quick disconnects were coupled to the bent stab. The bent stab provided the offset to allow the circuit breaker line terminal to be coupled to the vertical riser. This configuration has the disadvantage of requiring the vertical riser to be set back in the housing. As bus assemblies typically have the front edge of the vertical risers and runbacks laterally aligned, the bent stab device may not be used with many bus assemblies. Moreover, as only one set of conductors is set back, the bent stab may not be used on the terminal coupled to the forward conductors.
There is, therefore, a need for an offset assembly for a circuit breaker structured to be used with a bus assembly wherein the front edge of the vertical risers and the runbacks are laterally aligned.
There is a further need for an offset assembly for a circuit breaker that may be used on both the load terminals and the line terminals.
There is a further need for an offset assembly for a circuit breaker that is structured to be coupled to existing circuit breakers and bus assemblies.